EP0196447B1 - Process for enhancing the oxidation and corrosion resistance of a component made from a dispersion-hardened superalloy by means of a surface treatment - Google Patents

Process for enhancing the oxidation and corrosion resistance of a component made from a dispersion-hardened superalloy by means of a surface treatment Download PDF

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EP0196447B1
EP0196447B1 EP86102345A EP86102345A EP0196447B1 EP 0196447 B1 EP0196447 B1 EP 0196447B1 EP 86102345 A EP86102345 A EP 86102345A EP 86102345 A EP86102345 A EP 86102345A EP 0196447 B1 EP0196447 B1 EP 0196447B1
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component
zone
recrystallization
fine
grained
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German (de)
French (fr)
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EP0196447A1 (en
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Mohamed Yousef Dr. Nazmy
Hans Dr. Rydstad
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BBC Brown Boveri AG Switzerland
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F3/00—Changing the physical structure of non-ferrous metals or alloys by special physical methods, e.g. treatment with neutrons
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S148/00—Metal treatment
    • Y10S148/902—Metal treatment having portions of differing metallurgical properties or characteristics
    • Y10S148/903—Directly treated with high energy electromagnetic waves or particles, e.g. laser, electron beam

Definitions

  • the invention is based on a method for increasing the oxidation and corrosion resistance of a component made of a dispersion-hardened superalloy according to the preamble of claim 1 and claim 4.
  • High-temperature alloys especially superalloys, especially those with hardening dispersoids, are used under strict conditions regarding temperature, mechanical stress and corrosive or oxidizing atmosphere.
  • attempts are being made to increase their resistance to oxidation and corrosion by alloying with suitable elements or by applying protective layers.
  • these materials are used almost exclusively in the coarse-grained, preferably in the elongated, coarse-grained state (E. Auto and RF Singer, The effect of grain shape on stress rupture of the oxide dispersion strengthened superalloy INCONEL MA 6000, Seven Spring Conference on Superalloys, Conference Proceedings, The Metallurgical Society of AIME, 1984, pp. 367-376).
  • the invention has for its object to provide a method for increasing the oxidation and corrosion resistance of components made of a dispersion-hardened superalloy by means of a surface treatment, which does not affect the monolithic connection, is characterized by optimal properties of the surface layer and is simple on the finished component can be carried out economically.
  • a prismatic test specimen 100 mm long, 40 mm wide and 40 mm thick was cut from a medium-sized forging bar made of a dispersion-hardened nickel-based superalloy.
  • the alloy known under the trade name MA 6000 (INCO) had the following composition:
  • the surface zone 3 of a long side of the prismatic body was deformed over its entire width and over a length of 60 mm with a shot peening 2.
  • the pressure during shot peening was 0.8 MPa
  • the diameter of the steel balls was 0.3 to 0.6 mm
  • the total blasting time for the entire surface was 5 minutes.
  • the body was annealed at 1 280 ° C for 1 h.
  • the coarse-grain recrystallized core zone 4 had stalk-like elongated crystallites of 12 to 15 mm in length and 4 to 6 mm in width, while the fine-grain recrystallized surface zone 5 of 200 ⁇ m depth had an average grain size of less than 2 ⁇ m.
  • Fine-grained surface zones 5 of approximately 100 to 200 ⁇ m thick can be produced in the manner described.
  • the operating parameters for shot peening vary depending on the alloy to be treated, the structural condition of the starting material and the thickness of the fine-grained surface zone to be produced.
  • the sheet metal section was subjected to a one-time cold rolling process, with a total decrease in thickness from originally 4 mm to 3.9 mm (2.5%). This cold deformation mainly took place in the surface zones of the sheet.
  • the sheet section was subjected to recrystallization annealing at a temperature of 1,330 ° C. for 1/2 hour.
  • the coarse-grained recrystallized core zone showed elongated crystallites with an average length of 6 to 8 mm in length, 2 mm in width and 1 mm in thickness, while the fine-grained recrystallized surface zones with a depth of 150 ⁇ m had grain sizes of 2 to 5 ⁇ m.
  • the degree of cold deformation during rolling, rolling, pressing etc. can advantageously be set in such a way that it corresponds to a reduction in thickness of approximately 2 to 5% for such sheet, strip and sheet-shaped workpieces.
  • a turbine blade was manufactured from the material called MA 6000 (workpiece structure 12 in fine-grained condition).
  • the airfoil designed as a wing profile had a length of 220 mm, a width of 70 mm and a profile depth of 18 mm, with a max. Thickness of 12 mm.
  • the component was first cleaned, degreased and then hung in an electrochemical nickel bath.
  • a nickel layer 11 with a thickness of 50 ⁇ m was applied to the surface in a galvanic manner.
  • the workpiece was then subjected to diffusion annealing under a protective gas atmosphere at a temperature of 1,020 ° C. for 6 hours. This resulted in the surface zone 13 enriched with nickel.
  • the diffusion of nickel into the base material caused a certain grain growth, which can be influenced by the thickness of the nickel layer, the diffusion temperature and the diffusion time.
  • the diffusion layer reached an average thickness of 200 ⁇ m.
  • the controlled grain growth during the diffusion process had the result that the recrystallization annealing carried out subsequently according to Example I at 1 280 ° C./1 h resulted in a coarse-grained recrystallized core zone 4, while the surface zone 5 was obtained fine-grained. Extremely, there was still a thin, unchanged nickel-rich surface layer 14 as the rest. This surface layer 14 was finally removed electrolytically (see FIG. 9).
  • Nickel layers 11 can advantageously have a thickness of 10 to 50 ⁇ m. Diffusion annealing for the material MA 6000 can be carried out at temperatures between approx. 1 000 and 1 050 ° C for approx. 4 to 10 h.
  • the invention is not restricted to the exemplary embodiments.
  • the cold deformation of the surface can be carried out in addition to shot peening, surface rolling and pressing, drawing, thinning (in the case of hollow bodies) or in any other manner known per se.
  • the recrystallization annealing must be carried out in the range between the recrystallization and solidus temperature.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
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Abstract

1. A process for increasing the oxidation resistance and corrosion resistance of a component made of a dispersion strengthened superalloy by a surface treatment, characterised in that, regardless of the structural state of the starting material, the component is subjected to a surface treatment by coldworking, the degree of cold deformation in the surface zone (3, 5) being chosen so that, in the subsequent heat treatment, the available motive force leads to a fine-grained structure while the core zone (4) is forced to form coarse grains, and in that the component is subjected to recrystallization annealing in a temperature range above the recrystallization and below the solidus temperature.

Description

Die Erfindung geht aus von einem Verfahren zur Erhöhung des Oxydations- und Korrosionswiderstandes eines Bauteils aus einer dispersionsgehärteten Superlegierung nach der Gattung des Oberbegriffs des Anspruchs 1 und des Anspruchs 4.The invention is based on a method for increasing the oxidation and corrosion resistance of a component made of a dispersion-hardened superalloy according to the preamble of claim 1 and claim 4.

Hochwarmfeste Legierungen, insbesondere Superlegierungen, darunter vor allem solche mit härtenden Dispersoiden werden unter stets strengen Bedingungen betreffend Temperatur, mechanische Beanspruchung und korrosive oder oxydierende Atmosphäre eingesetzt. Man versucht allgemein ihren Oxydationsund Korrosionswiderstand durch Zulegieren von geeigneten Elementen oder durch Aufbringen von Schutzschichten zu erhöhen. Diesen Massnahmen sind jedoch Grenzen gesetzt. Um beste Warmfestigkeit bei höchsten Temperaturen zu erreichen, werden diese Werkstoffe fast ausschliesslich im grobkömigen, bevorzugt im längsgestreckten grobkömigen Zustand eingesetzt (E. Arzt und R.F. Singer, The effect of grain shape on stress rupture of the oxide dispersion strengthened superalloy INCONEL MA 6000, Seven Spring Conference on Superalloys, Conference Proceedings, The Metallurgical Society of AIME, 1984, pp. 367-376).High-temperature alloys, especially superalloys, especially those with hardening dispersoids, are used under strict conditions regarding temperature, mechanical stress and corrosive or oxidizing atmosphere. In general, attempts are being made to increase their resistance to oxidation and corrosion by alloying with suitable elements or by applying protective layers. However, there are limits to these measures. In order to achieve the best heat resistance at the highest temperatures, these materials are used almost exclusively in the coarse-grained, preferably in the elongated, coarse-grained state (E. Arzt and RF Singer, The effect of grain shape on stress rupture of the oxide dispersion strengthened superalloy INCONEL MA 6000, Seven Spring Conference on Superalloys, Conference Proceedings, The Metallurgical Society of AIME, 1984, pp. 367-376).

Es hat sich andererseits gezeigt, dass feinkörniges Material ein günstigeres Verhalten gegen Korrosion und Oxydation aufweist (C.S. Giggins, F.S. Pettit, « The effect of alloy grain size and surface deformation on the selective oxidation of chromium in nickelchromium alloys at temperatures of 900 and 1 100 °C », Trans. TMS-AIME, 245, Seite 2 509, 1969).On the other hand, it has been shown that fine-grained material has a more favorable behavior against corrosion and oxidation (CS Giggins, FS Pettit, «The effect of alloy grain size and surface deformation on the selective oxidation of chromium in nickelchromium alloys at temperatures of 900 and 1 100 ° C », Trans. TMS-AIME, 245, page 2 509, 1969).

In dispersionsgehärteten Legierungen wurde nach einer gewissen Zeit der Einwirkung einer oxydierenden Atmosphäre die Bildung von Poren unter der Werkstückoberfläche festgestellt. Diese unerwünschte Porenentwicklung ist unter anderem von der Gefügeausbildung, insbesondere von der Korngrösse abhängig. Grobes Korn begünstigt die Porenbildung, feines Korn hemmt sie (J.H. Weber and P.S. Gilman, environmentally induced porosity in Ni-Cr and Ni-Cr oxide dispersion strengthened alloys, Scripta Metallurgica Vol. 18, p. 479-482, 1984; LK. Glasgow, G.J. Santoro, and M.A. Gedwill, « Oxidation + Hot Corrosion of Coated and Bare Oxide Dispersion Strengthened Superalloys », in Frontiers of High Temperature Materials, J. Benjamin ed. Inco. 1981).After a certain period of exposure to an oxidizing atmosphere, the formation of pores under the workpiece surface was found in dispersion-hardened alloys. This undesirable pore development depends, among other things, on the structure, in particular on the grain size. Coarse grain favors pore formation, fine grain inhibits it (JH Weber and PS Gilman, environmentally induced porosity in Ni-Cr and Ni-Cr oxide dispersion strengthened alloys, Scripta Metallurgica Vol. 18, p. 479-482, 1984; LK. Glasgow , GJ Santoro, and MA Gedwill, "Oxidation + Hot Corrosion of Coated and Bare Oxide Dispersion Strengthened Superalloys", in Frontiers of High Temperature Materials, J. Benjamin ed. Inco. 1981).

In diesem Zusammenhang ist schon vorgeschlagen worden, ein Bauteil mit grobkörnigem Kern und feinkörniger Randzone zu erzeugen (Vergl. EP-A-115 092). Diese Möglichkeit wird jedoch nur sehr beschränkt und unvollkommen ausgenützt.In this connection, it has already been proposed to produce a component with a coarse-grained core and fine-grained edge zone (cf. EP-A-115 092). However, this possibility is only used to a very limited extent and incompletely.

Es ist bekannt, dass bei Nickelbasis-Superlegierungen durch Laserumschmelzen der Oberflächenzone eine Komverfeinerung und die Ausmerzung der p.-Phase erreicht werden kann. Dies resultiert in einer Erhöhung des Korrosions- und Oxydationswiderstandes der Werkstückoberfläche (Vergl. M.F. Chen et al, « Elimination of p. phase and improvement of hot corrosion resistance of a nickel-base superalloy by laserglazing », High temperature technology, Vol. 3, No. 1, 1985, Guildford, Surney, G.B.).It is known that in the case of nickel-based superalloys, laser refinement of the surface zone can achieve a refinement and the eradication of the p-phase. This results in an increase in the corrosion and oxidation resistance of the workpiece surface (see MF Chen et al, “Elimination of p. Phase and improvement of hot corrosion resistance of a nickel-base superalloy by laser glazing”, High temperature technology, Vol. 3, No. 1, 1985, Guildford, Surney, GB).

Es besteht daher ein grosses Bedürfnis, nach weiteren Möglichkeiten zur Verbesserung der Hochtemperaturbeständigkeit von Bauteilen aus Superlegierungen unter oxydierenden und korrodierenden Einflüssen.There is therefore a great need for further possibilities for improving the high temperature resistance of components made of superalloys under oxidizing and corrosive influences.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Erhöhung des Oxydations- und Korrosionswiderstandes von Bauteilen aus einer dispersionsgehärteten Superlegierung mittels einer Oberflächenbehandlung anzugeben, welches den monolithischen Zusammenhang nicht beeinträchtigt, sich durch optimale Eigenschaften der Oberflächenschicht auszeichnet und sich in einfacher Weise am fertig geformten Bauteil wirtschaftlich durchführen lässt.The invention has for its object to provide a method for increasing the oxidation and corrosion resistance of components made of a dispersion-hardened superalloy by means of a surface treatment, which does not affect the monolithic connection, is characterized by optimal properties of the surface layer and is simple on the finished component can be carried out economically.

Diese Aufgabe wird durch die im kennzeichnenden Teil der Ansprüche 1 und 4 angegebenen Merkmale gelöst.This object is achieved by the features specified in the characterizing part of claims 1 and 4.

Die Erfindung wird anhand der nachfolgenden, durch Figuren näher erläuterten Ausführungsbeispiele beschrieben.The invention is described on the basis of the following exemplary embodiments which are explained in more detail by means of figures.

Dabei zeigt :

  • Fig. 1 ein schematisches Schliffbild durch ein Bauteil im Anlieferungszustand mit Behandlung der Oberflächenzone durch einen Kugelstrahl,
  • Fig. 2 ein schematisches Schliffbild durch ein Bauteil nach der Behandlung der Oberflächenzone durch Kugelstrahlen und nach der Rekristallisationglühung,
  • Fig. 6 ein schematisches Schliffbild durch ein Bauteil im Anlieferungszustand mit elektrolytisch aufgebrachter Nickelschicht,
  • Fig. 7 ein schematisches Schliffbild durch ein Bauteil mit Nickelschicht nach einer Diffusionsglühung,
  • Fig. 8 ein schematisches Schliffbild durch ein Bauteil mit Nickelschicht nach einer Diffusions- und einer Rekristallisationsglühung,
  • Fig. 9 ein schematisches Schliffbild durch ein Bauteil nach einer Diffusions- und Rekristallisationsglühung, nach der Entfernung der nickelreichen Oberflächenschicht.
It shows:
  • 1 is a schematic micrograph of a component in the delivery state with treatment of the surface zone by a shot peening,
  • 2 shows a schematic micrograph of a component after the treatment of the surface zone by shot peening and after the recrystallization annealing,
  • 6 shows a schematic micrograph of a component in the delivery state with an electrolytically applied nickel layer,
  • 7 shows a schematic micrograph through a component with a nickel layer after diffusion annealing,
  • 8 shows a schematic micrograph through a component with a nickel layer after diffusion and recrystallization annealing,
  • 9 shows a schematic micrograph of a component after diffusion and recrystallization annealing, after removal of the nickel-rich surface layer.

In Fig. 1 ist schematisch ein Schliffbild durch ein Bauteil im Anlieferungszustand bei der Behandlung der Oberflächenzone durch einen Kugelstrahl dargestellt. 1 ist das mittel- bis feinkörnige Werkstückgefüge im Anlieferungszustand (z. B. Strangpress- Walz- oder Schmiedeerzeugnis). Die Korngrösse ist hierbei im allgemeinen nicht sehr kritisch. Das Gefüge ist jedoch an die Bedingung gebunden, dass es genügend Triebkraft zur Grobkornbildung nach der abschliessenden Rekristallisationsglühung besitzt. 2 ist ein Kugelstrahl, welcher zur Kaltwerformung der Oberfläche dient, wogegen 3 die bereits durch Kugelstrahlen verformte Oberflächenzone des Werkstücks darstellt. Die Vorschubrichtung des Kugelstrahls 2 ist durch einen Pfeil angedeutet.

  • Fig. 2 beinhaltet ein schematisches Schliffbild durch ein gemäss Fig. 1 behandeltes Bauteil, d. h. nach der Behandlung der Oberflächenzone durch Kugelstrahlen und nach einer zusätzlichen Rekristallisationsglühung. 4 stellt die grobkömig rekristallisierte Kernzone, 5 die feinkörnig rekristallisierte, zuvor verformte Oberflächenzone dar.
  • In Fig. 6 ist schematisch ein Schliffbild durch ein Bauteil im Anlieferungszustand mit elektrolytisch aufgebrachter Nickelschicht dargestellt. 12 ist das feinkörnige Werkstoffgefüge im Anlieferungszustand. 11 ist die - in der Dicke stark übetrieben gezeichnete - elektrolytisch aufgebrachte Nickelschicht.
  • Fig. 7 zeigt ein schematisches Schliffbild durch ein Bauteil mit Nickelschicht nach einer Diffusionsglühung. 12 ist das unveränderte feinkörnige Werkstoffgefüge, 13 die an Nickel durch Diffusion angereicherte Oberflächenzone des Werkstücks.
  • Fig. 8 stellt schematisch ein Schliffbild durch ein Bauteil mit Nickelschicht nach einer Diffusions- und einer Rekristallisationsglühung dar. Auf die grobkörnig rekristallisierte Kemzone 4 folgt zunächst die feinkörnig rekristallisierte Oberflächenzone 5 und zuletzt die eigentliche, nickelreiche Oberflächenschicht 14, die an der Werkstückoberfläche unter Umständen noch aus reinem Nickel bestehen kann.
  • In Fig. 9 ist ein schematisches Schliffbild durch ein Bauteil nach einer Diffusions- und Rekristallisationsglühung gemäss Fig. 8, nach zusätzlicher Entfernung der nickelreichen Oberflächenschicht 14 dargestellt. Die übrigen Bezugszeichen entsprechen denjenigen der Fig. 8.
1 schematically shows a micrograph of a component in the delivery state when the surface zone is treated by a shot peening. 1 is the medium to fine-grained workpiece structure as delivered (e.g. extruded, rolled or forged product). The grain size is generally not very critical. However, the structure is tied to the condition that it has sufficient driving force to form coarse grains after the final recrystallization annealing. 2 is a Shot peening, which is used for cold forming the surface, whereas 3 represents the surface zone of the workpiece that has already been deformed by shot peening. The direction of advance of the ball jet 2 is indicated by an arrow.
  • FIG. 2 contains a schematic micrograph of a component treated according to FIG. 1, ie after the surface zone has been treated by shot peening and after an additional recrystallization annealing. 4 represents the coarse-grained recrystallized core zone, 5 the fine-grained recrystallized, previously deformed surface zone.
  • 6 schematically shows a micrograph of a component in the delivery state with an electrolytically applied nickel layer. 12 is the fine-grained material structure in the delivery state. 11 is the electrolytically applied nickel layer, which is markedly exaggerated in thickness.
  • 7 shows a schematic micrograph through a component with a nickel layer after diffusion annealing. 12 is the unchanged fine-grained material structure, 13 the surface zone of the workpiece enriched in nickel by diffusion.
  • 8 schematically shows a micrograph of a component with a nickel layer after diffusion and recrystallization annealing. The coarse-grain recrystallized core zone 4 is first followed by the fine-grain recrystallized surface zone 5 and finally the actual, nickel-rich surface layer 14, which may still be on the workpiece surface can consist of pure nickel.
  • FIG. 9 shows a schematic micrograph of a component after diffusion and recrystallization annealing according to FIG. 8, after additional removal of the nickel-rich surface layer 14. The remaining reference numerals correspond to those in FIG. 8.

Ausführungsbeispiel IEmbodiment I

Siehe Fig. 1 und 2.See Figs. 1 and 2.

Aus einem mit mittlerer Korngrösse vorliegenden Schmiedebarren aus einer dispersionsgehärteten Nickelbasis-Superlegierung wurde ein prismatischer Probekörper von 100 mm Länge, 40 mm Breite und 40 mm Dicke abgeschnitten. Die unter dem Handelsnamen MA 6000 (INCO) bekannte Legierung hatte die nachfolgende Zusammensetzung:

Figure imgb0001
A prismatic test specimen 100 mm long, 40 mm wide and 40 mm thick was cut from a medium-sized forging bar made of a dispersion-hardened nickel-based superalloy. The alloy known under the trade name MA 6000 (INCO) had the following composition:
Figure imgb0001

Die Oberflächenzone 3 einer Längsseite des prismatischen Körpers wurde auf ihrer ganzen Breite und über eine Länge von 60 mm mit einem Kugelstrahl 2 verformt. Der Druck beim Kugelstrahlen betrug 0,8 MPa, der Durchmesser der Stahlkugeln 0,3 bis 0,6 mm, die Strahlzeit insgesamt für die ganze Fläche 5 min. Nach dem Kugelstrahlen wurde der Körper während 1 h bei einer Temperatur von 1 280 °C geglüht. Die grobkömig rekristallisierte Kemzone 4 wies stengelartig gestreckte Kristallite von 12 bis 15 mm Länge und 4 bis 6 mm Breite auf, während die feinkörnig rekristallisierte Oberflächenzone 5 von 200 Am Tiefe eine durchschnittliche Komgrösse von weniger als 2 Am zeigte.The surface zone 3 of a long side of the prismatic body was deformed over its entire width and over a length of 60 mm with a shot peening 2. The pressure during shot peening was 0.8 MPa, the diameter of the steel balls was 0.3 to 0.6 mm, the total blasting time for the entire surface was 5 minutes. After shot peening, the body was annealed at 1 280 ° C for 1 h. The coarse-grain recrystallized core zone 4 had stalk-like elongated crystallites of 12 to 15 mm in length and 4 to 6 mm in width, while the fine-grain recrystallized surface zone 5 of 200 μm depth had an average grain size of less than 2 μm.

In der beschriebenen Weise können feinkörnige Oberflächenzonen 5 von ca. 100 bis 200 µm Dicke hergestellt werden. Die Betriebsparameter für das Kugelstrahlen variieren je nach zu behandelnder Legierung, Gefügezustand des Ausgangsmaterials und Dicke der herzustellenden feinkörnigen Oberflächenzone.Fine-grained surface zones 5 of approximately 100 to 200 μm thick can be produced in the manner described. The operating parameters for shot peening vary depending on the alloy to be treated, the structural condition of the starting material and the thickness of the fine-grained surface zone to be produced.

Ausführungsbeispiel IIEmbodiment II

Aus einem feinkörnigen Blech aus einer dispersionsgehärteten Nickelbasis-Superlegierung wurde ein rechteckiges Stück mit den Dimensionen 4 x 100 x 30 mm herausgeschnitten. Der unter dem Handelsnamen MA 754 (INCO) laufende Werkstoff hatte folgende Zusammensetzung :

Figure imgb0002
A rectangular piece with the dimensions 4 x 100 x 30 mm was cut out of a fine-grained sheet made of a dispersion-hardened nickel-based superalloy. The material running under the trade name MA 754 (INCO) had the following composition:
Figure imgb0002

Der Blechabschnitt wurde einem einmaligen Kaltwalzprozess unterworfen, wobei eine totale Dickenabnahme von ursprünglich 4 mm auf 3,9 mm (2,5 %) eingestellt wurde. Diese Kaltverformung fand überwiegend in den Oberflächenzonen des Bleches statt. Nach dem Kaltwalzen wurde der Blechabschnitt während 1/2 h einer Rekristallisationsglühung bei einer Temperatur von 1 330°C ausgesetzt. Die grobkörnig rekristallisierte Kemzone zeigte längsgestreckte Kristallite von durchschnittlich 6 bis 8 mm Länge, 2 mm Breite und 1 mm Dicke, während die feinkörnig rekristallisierten Oberflächenzonen von 150 µm Tiefe Korngrössen von 2 bis 5 µm aufwiesen.The sheet metal section was subjected to a one-time cold rolling process, with a total decrease in thickness from originally 4 mm to 3.9 mm (2.5%). This cold deformation mainly took place in the surface zones of the sheet. After cold rolling, the sheet section was subjected to recrystallization annealing at a temperature of 1,330 ° C. for 1/2 hour. The coarse-grained recrystallized core zone showed elongated crystallites with an average length of 6 to 8 mm in length, 2 mm in width and 1 mm in thickness, while the fine-grained recrystallized surface zones with a depth of 150 µm had grain sizes of 2 to 5 µm.

Der Kaltverformungsgrad beim Walzen, Rollen, Drücken etc. kann in vorteilhafter Weise derart eingestellt werden, dass er für derartige blech-, band- und tafelförmige Werkstücke ca. 2 bis 5 % Dickenabnahme entspricht.The degree of cold deformation during rolling, rolling, pressing etc. can advantageously be set in such a way that it corresponds to a reduction in thickness of approximately 2 to 5% for such sheet, strip and sheet-shaped workpieces.

Ausführungsbeispiel VEmbodiment V

Vergleiche Figuren 6, 7, 8 und 9.Compare Figures 6, 7, 8 and 9.

Aus dem Werkstoff mit der Bezeichnung MA 6000 wurde eine Turbinenschaufel gefertigt (Werkstückgefüge 12 in feinkörnigem Zustand). Das als Tragflügelprofil ausgelegte Schaufelblatt hatte eine Länge von 220 mm, eine Breite von 70 mm und eine Profiltiefe von 18 mm, bei einer max. Dicke von 12 mm. Das Bauteil wurde zunächst gereinigt, entfettet und hierauf in ein elektrochemisches Nickelbad eingehängt. Auf galvanische Weise wurde auf der Oberfläche eine Nickelschicht 11 von 50 µm Dicke aufgebracht. Dann wurde das Werkstück während 6 h einer Diffusionsglühung unter Schutzgasatmosphäre bei einer Temperatur von 1 020 °C unterworfen. Hierbei entstand die an Nickel angereicherte Oberflächenzone 13. Die Diffusion von Nickel in den Grundwerkstoff verursachte ein gewisses Komwachstum, welches durch die Dicke der Nickelschicht, die Diffusionstemperatur und die Diffusionszeit beeinflusst werden kann. Die Diffusionsschicht erreichte im vorliegenden Fall eine Dicke von durchschnittlich 200 µm. Das kontrollierte Kornwachstum während des Diffusionsprozesses hatte zur Folge, dass die nachträglich gemäss Beispiel I bei 1 280 °C/1 h durchgeführte Rekristallisationsglühung eine grobkörnig rekristallisierte Kemzone 4 ergab, während die Oberflächenzone 5 feinkörnig anfiel. Zu äusserst war noch eine dünne, unverändert vorliegende nickelreiche Oberflächenschicht 14 als Rest vorhanden. Diese Oberflächenschicht 14 wurde schliesslich auf elektrolytischem Wege entfernt (Siehe Fig. 9).A turbine blade was manufactured from the material called MA 6000 (workpiece structure 12 in fine-grained condition). The airfoil designed as a wing profile had a length of 220 mm, a width of 70 mm and a profile depth of 18 mm, with a max. Thickness of 12 mm. The component was first cleaned, degreased and then hung in an electrochemical nickel bath. A nickel layer 11 with a thickness of 50 μm was applied to the surface in a galvanic manner. The workpiece was then subjected to diffusion annealing under a protective gas atmosphere at a temperature of 1,020 ° C. for 6 hours. This resulted in the surface zone 13 enriched with nickel. The diffusion of nickel into the base material caused a certain grain growth, which can be influenced by the thickness of the nickel layer, the diffusion temperature and the diffusion time. In the present case, the diffusion layer reached an average thickness of 200 μm. The controlled grain growth during the diffusion process had the result that the recrystallization annealing carried out subsequently according to Example I at 1 280 ° C./1 h resulted in a coarse-grained recrystallized core zone 4, while the surface zone 5 was obtained fine-grained. Extremely, there was still a thin, unchanged nickel-rich surface layer 14 as the rest. This surface layer 14 was finally removed electrolytically (see FIG. 9).

Nickelschichten 11 können vorteilhafterweise eine Dicke von 10 bis 50 µm aufweisen. Die Diffusionsglühung für den Werkstoff MA 6000 kann bei Temperaturen zwischen ca. 1 000 und 1 050 °C während ca. 4 bis 10 h durchgeführt werden.Nickel layers 11 can advantageously have a thickness of 10 to 50 μm. Diffusion annealing for the material MA 6000 can be carried out at temperatures between approx. 1 000 and 1 050 ° C for approx. 4 to 10 h.

Die Erfindung ist nicht auf die Ausführungsbeispiele beschränkt.The invention is not restricted to the exemplary embodiments.

Die Kaltverformung der Oberfläche kann ausser durch Kugelstrahlen, Oberflächenwalzen und Drücken, durch Ziehen, Aufdornen (bei Hohlkörpern) oder auf irgend eine andere, an sich bekannte Art und Weise erfolgen. Die Rekristallisationsglühung ist im Bereich zwischen Rekristallisations- und Solidustemperatur durchzuführen.The cold deformation of the surface can be carried out in addition to shot peening, surface rolling and pressing, drawing, thinning (in the case of hollow bodies) or in any other manner known per se. The recrystallization annealing must be carried out in the range between the recrystallization and solidus temperature.

BezeichnungslisteLabel list

  • 1 = Werkstückgefüge im Anlieferungszustand (mittel- bis feinkömig)1 = workpiece structure as delivered (medium to fine-grained)
  • 2 = Kugelstrahl2 = shot peening
  • 3 = Durch Kugelstrahlen verformte Oberfiächenzone3 = surface zone deformed by shot peening
  • 4 = Grobkörnig rekristallisierte Kemzone4 = coarse-grained recrystallized core zone
  • 5 = Feinkörnig rekristallisierte Oberflächenzone5 = fine-grained recrystallized surface zone
  • 11 = Nickelschicht11 = nickel layer
  • 12 = Werkstückgefüge im Anlieferungszustand (feinkörnig)12 = workpiece structure as delivered (fine-grained)
  • 13 = An Nickel durch Diffusion angereicherte Oberflächenzone13 = Surface zone enriched in nickel by diffusion
  • 14 = Nickelreiche Oberflächenschicht14 = surface layer rich in nickel

Claims (4)

1. A process for increasing the oxidation resistance and corrosion resistance of a component made of a dispersion strengthened superalloy by a surface treatment, characterised in that, regardless of the structural state of the starting material, the component is subjected to a surface treatment by cold- working, the degree of cold deformation in the surface zone (3, 5) being chosen so that, in the subsequent heat treatment, the available motive force leads to a fine-grained structure while the core zone (4) is forced to form coarse grains, and in that the component is subjected to recrystallization annealing in a temperature range above the recrystallization and below the solidus temperature.
2. A process according to claim 1, characterised in that working of the surface zone (3, 5) is carried out by means of a stream of shot (2).
3. A process according to claim 1, characterised in that working of the surface zone (5) is carried out by means of surface milling or pressing.
4. A process for increasing the oxidation resistance and corrosion resistance of a component made of a dispersion strengthened superalloy by means of a surface-treatment, characterised in that, starting from a fine-grained structural state of the starting material which has been hot-worked beforehand, the component is provided with a 10 to 50 ¡.a.m thick nickel layer (1) (sic) applied by electroplating and is then heated to a temperature below the recrystallization temperature of the material in order to effect diffusion of the nickel into the interior and to produce a nickel-rich surface zone (13), and in that the component is cooled and then heated to a temperature above the recrystallization temperature, the core zone (4) being forced to form coarse grains while the surface zone (5) is prevented by a lack of motive force from undergoing secondary recrystallization, and is forced to retain the original fine-grained state.
EP86102345A 1985-03-15 1986-02-24 Process for enhancing the oxidation and corrosion resistance of a component made from a dispersion-hardened superalloy by means of a surface treatment Expired EP0196447B1 (en)

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CH1166/85 1985-03-15
CH116685 1985-03-15

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DE3664930D1 (en) 1989-09-14
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JPS61213360A (en) 1986-09-22

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